1. Field of the Invention
The present invention relates to a three-dimensional hologram image display apparatus and a three-dimensional hologram image display system, each of which displays a three-dimensional hologram image by use of computed interference fringe patterns (computer generated hologram).
2. Description of the Related Art
Conventionally, a three-dimensional hologram image display apparatus has been known, which irradiates a reference wave onto a computer generated hologram displayed (played back) on a liquid crystal display (LCD) so as to reproduce an object wave, thus displaying a three-dimensional hologram image. Note that the computer generated hologram consists of interference fringe patterns obtained by a computation.
Specifically, as shown in FIG. 1, such interference fringe patterns are created from the object wave and the reference wave. The object wave is created in a manner that a laser beam irradiated onto an object of a three-dimensional shape is reflected thereon.
However, in such a conventional three-dimensional hologram image display apparatus, resolution of the LCD has limitations, and there has been a problem in that sufficient resolution for displaying a three-dimensional hologram image of the object of the three-dimensional shape cannot be obtained.
Specifically, resolution of 1 μm or less is required for displaying the three-dimensional hologram image of the object of the three-dimensional shape. However, even the highest-definition LCD at present only has resolution of approximately 10 μm.
Therefore, only a field of view (a range where the three-dimensional hologram image can be actually observed) with a width of several centimeters can be ensured, when an observer observes the three-dimensional hologram image from a point apart therefrom by 50 cm.
Accordingly, there has been a problem in that the conventional three-dimensional hologram image display apparatus does not have the sufficient resolution for displaying the three-dimensional hologram image of the object of the three-dimensional shape.
As a result, the conventional three-dimensional hologram image display apparatus has had a problem in that the three-dimensional hologram image of the object of the three-dimensional shape can be observed only by use of a peephole system having a narrow field of view.
In order to solve the problem described above, a three-dimensional hologram image display system using photorefractive crystal has been known as a system which supplement limitations of the resolution of the LCD (restrictions of the field of view).
A principle of such a three-dimensional hologram image display system will be briefly described below with reference to FIG. 2.
As shown in FIG. 2, the three-dimensional hologram image display system is configured with an interference fringe pattern computing apparatus 1, an interference fringe pattern recording apparatus 2a, reference wave irradiation apparatuses 3a and 3b, and an interference fringe pattern display apparatus 4.
The interference fringe pattern computing apparatus 1 is configured with a computer 11. As shown in FIG. 1, the interference fringe pattern computing apparatus 1 is configured to compute the interference fringe patterns (computer generated hologram) created from the object wave and the reference wave.
The interference fringe pattern display apparatus 4 is configured with an electronic display device (LCD 12 in an example of FIG. 2). The interference fringe pattern display apparatus 4 is configured to display an image of the interference fringe patterns computed by the interference fringe pattern computing apparatus 1.
Information for displaying such an image of the interference fringe patterns is transmitted from the interference fringe pattern computing apparatus 1 to the interference fringe pattern display apparatus 4 by an image signal.
The reference wave irradiation apparatus 3a is configured to irradiate a reference wave B1 toward the interference fringe pattern display apparatus 4 (LCD 12), and the reference wave irradiation apparatus 3b is configured to irradiate a reference wave B2 toward the interference fringe pattern recording apparatus 2a (hologram recording device 21).
Here, the reference wave B1 has the same wavelength and incidence angle as those of the reference wave for use in the computation of the interference fringe patterns by the interference fringe pattern computing apparatus 1.
When the reference wave B1 is irradiated toward the interference fringe pattern display apparatus 4, a direct beam and an object wave A1 are generated from the interference fringe pattern display apparatus 4. Here, the object wave A1 has a beam wavefront equivalent to that of the object wave for use in the computation of the interference fringe patterns by the interference fringe pattern computing apparatus 1. The object wave A1 propagates to the interference fringe pattern recording apparatus 2a. 
The interference fringe pattern recording apparatus 2a is configured with the hologram recording device (light modulation device) 21. The interference fringe pattern recording apparatus 2a is configured to record an interference fringe patterns created from the object wave A1 and the reference wave B2 irradiated from the reference wave irradiation apparatus 3a, in the hologram recording device 21. Here, as the hologram recording device 21, the photorefractive crystal is used.
In a state where the interference fringe patterns are recorded in the hologram recording device 21 (photorefractive crystal) as described above, when the object wave A1 from the interference fringe pattern display apparatus 4 is blocked by a shutter or the like, and only the reference wave B2 is irradiated toward the interference fringe pattern recording apparatus 2a, an object wave A2 is generated by the interference fringe patterns recorded in the hologram recording device 21.
As a result, the observer can three-dimensionally observe the above-mentioned image of the three-dimensional shape by means of the object wave A2.
Such a three-dimensional hologram image display system using the photorefractive crystal as the hologram recording device 21 rerecords the interference fringe patterns created from the object wave A1 played back by the LCD and from the reference wave B2, thus making it possible to achieve an enlargement of the field of view.
However, the conventional three-dimensional hologram image display system using the photorefractive crystal is configured to record the interference fringe patterns in the interference fringe pattern recording apparatus 2a by use of an optical technique.
Accordingly, the conventional three-dimensional hologram image display system has had a problem in that the conventional three-dimensional hologram image display system is difficult to downsize.